factor out layer checking; use slices.Reverse to check for descending levels

2024/day02.go

@@ -4,6 +4,7 @@ import (
 	"bufio"
 	"fmt"
 	"io"
+	"slices"
 	"strings"
 )
 
@@ -13,7 +14,6 @@ func (d Day2) Part1(r io.Reader) string {
 	s := bufio.NewScanner(r)
 	var sum int
 
-Scan:
 	for s.Scan() {
 
 		sz := strings.Count(s.Text(), " ") + 1
@@ -26,21 +26,13 @@ Scan:
 
 		fmt.Sscan(s.Text(), levelprts...)
 
-		increasing := level[1]-level[0] > 0
-		if increasing {
-			for i := 0; i < len(level)-1; i++ {
-				if diff := level[i+1] - level[i]; diff > 3 || diff < 1 {
-					continue Scan
-				}
-			}
+		if layerOk(level) {
 			sum++
 		} else {
-			for i := 0; i < len(level)-1; i++ {
-				if diff := level[i] - level[i+1]; diff > 3 || diff < 1 {
-					continue Scan
-				}
+			slices.Reverse(level)
+			if layerOk(level) {
+				sum++
 			}
-			sum++
 		}
 	}
 
@@ -124,3 +116,12 @@ Scan:
 func inrange(i int) bool {
 	return i < 4 && i > 0
 }
+
+func layerOk(layer []int) bool {
+	for i := 0; i < len(layer)-1; i++ {
+		if !inrange(layer[i] - layer[i+1]) {
+			return false
+		}
+	}
+	return true
+}